Bone's constraint limit X axis rotation more than 180° doesn't work
The values for the Rotation Limit Constraint are clamped 180 to -180. This is a known limitation. An example:



As soon as i try to rotate the bone beyond 180° the bone snaps back to 0°

You can find more about this in the Blender manual about Limit Rotation.

Note: There is a small chance that this limitation will be released some time in the future. You can find more about that in the bf-animsys mailing list.